package com.reformer.commons.utils;

import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;

/**
 * MD5工具类
 *
 * @author sdc
 */
public class MD5 {

    private static final String[] hexDigits = {"0", "1", "2", "3", "4", "5", "6", "7", "8", "9", "a", "b", "c", "d", "e", "f"};

    private MD5() {
    }

    /**
     * 转换字节数组为16进制字串
     *
     * @param b 字节数组
     * @return 16进制字串
     */
    public static String byteArrayToHexString(byte[] b) {
        StringBuilder resultSb = new StringBuilder();
        for (byte e : b) {
            resultSb.append(byteToHexString(e));
        }
        return resultSb.toString();
    }

    /**
     * 转换byte到16进制
     *
     * @param b 要转换的byte
     * @return 16进制格式
     */
    private static String byteToHexString(byte b) {
        int n = b;
        if (n < 0) {
            n = 256 + n;
        }
        int d1 = n / 16;
        int d2 = n % 16;
        return hexDigits[d1] + hexDigits[d2];
    }

    /**
     * MD5编码
     *
     * @param origin  原始字符串
     * @param charset 字符集
     * @return 经过MD5加密之后的结果
     */
    public static String encodeMD5(String origin, String charset) {
        char[] hexDigits = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F'};
        try {
            byte[] btInput = origin.getBytes(charset);
            // 获得MD5摘要算法的 MessageDigest 对象
            MessageDigest md = MessageDigest.getInstance("MD5");
            // 使用指定的字节更新摘要
            md.update(btInput);
            // 获得密文
            byte[] tmp = md.digest();
            // 把密文转换成十六进制的字符串形式
            int j = tmp.length;
            char[] str = new char[j * 2];
            int k = 0;
            for (int i = 0; i < j; i++) {
                byte byte0 = tmp[i];
                str[k++] = hexDigits[byte0 >>> 4 & 0xf];
                str[k++] = hexDigits[byte0 & 0xf];
            }
            return new String(str);
        } catch (Exception e) {
            e.printStackTrace();
            return null;
        }
    }

    /**
     * MD5编码
     *
     * @param origin 原始字符串
     * @return 经过MD5加密之后的结果
     */
    public static String encodeMD5(String origin) {
        String resultString = null;
        try {
            resultString = origin;
            MessageDigest md = MessageDigest.getInstance("MD5");
            resultString = byteArrayToHexString(md.digest(resultString.getBytes("UTF-8")));
        } catch (Exception e) {
            e.printStackTrace();
        }
        return resultString;
    }

    /**
     * md5指纹
     * @param bytes
     * @return
     */
    public static String encodeMD5(byte[] bytes) {
        String resultString = null;
        try {
            MessageDigest md = MessageDigest.getInstance("MD5");
            resultString = byteArrayToHexString(md.digest(bytes));
        } catch (Exception e) {
            e.printStackTrace();
        }
        return resultString;
    }
    /**
     * 加盐MD5
     *
     * @param origin 原始字符串
     * @return 返回加盐后的md5值
     */
    public static String encodeMD5WithSalt(String origin) {
        SecureRandom random;
        try {
            random = SecureRandom.getInstance("SHA1PRNG");
        } catch (NoSuchAlgorithmException e) {
            random = new SecureRandom();
        }
        StringBuffer sb = new StringBuffer(16);
        sb.append(random.nextInt(99999999)).append(random.nextInt(99999999));
        int len = sb.length();
        if (len < 16) {
            for (int i = 0; i < 16 - len; i++) {
                sb.append("0");
            }
        }
        String salt = sb.toString();
        origin = md5Hex(origin + salt);
        char[] cs = new char[48];
        for (int i = 0; i < 48; i += 3) {
            cs[i] = origin.charAt(i / 3 * 2);
            char c = salt.charAt(i / 3);
            cs[i + 1] = c;
            cs[i + 2] = origin.charAt(i / 3 * 2 + 1);
        }
        return new String(cs);
    }

    /**
     * 校验加盐后是否和原文一致
     *
     * @param origin    原字符串
     * @param md5Cipher md5值
     * @return 验证结果
     */
    public static boolean verify(String origin, String md5Cipher) {
        char[] cs1 = new char[32];
        char[] cs2 = new char[16];
        for (int i = 0; i < 48; i += 3) {
            cs1[i / 3 * 2] = md5Cipher.charAt(i);
            cs1[i / 3 * 2 + 1] = md5Cipher.charAt(i + 2);
            cs2[i / 3] = md5Cipher.charAt(i + 1);
        }
        String salt = new String(cs2);
        return md5Hex(origin + salt).equals(new String(cs1));
    }

    /**
     * 获取十六进制字符串形式的MD5摘要
     */
    private static String md5Hex(String src) {
        try {
            MessageDigest md5 = MessageDigest.getInstance("MD5");
            byte[] bs = md5.digest(src.getBytes("UTF-8"));
            return byteArrayToHexString(bs);
        } catch (Exception e) {
            return null;
        }
    }

}
